Typically, videoconferencing is implemented over dedicated Integrated Services Digital Network (ISDN) and/or T1/T3 circuits. These circuits provide a dedicated path between two geographically separate locations. A drawback to such an arrangement is that dedicated circuits can be extremely expensive and underutilized. There is a lot of wasted bandwidth if the dedicated circuits are not being utilized because a videoconference session is not taking place. Many corporations that have geographically separate locations typically have dedicated circuits (e.g., T1 circuits) providing a data network between them. The dedicated circuits allow the Local Area Networks (LAN) of each location to be connected together creating a Wide Area Network (WAN). The primary use of these circuits is for data connectivity between the two locations.
The LANs at each location are connected locally by Ethernet switches. The LANs provide an infrastructure with large amounts of bandwidth. The typical connectivity bandwidth on a LAN is 100 Mbps (full-duplex). This typically translates into excess amounts of bandwidth available between the end nodes and the router that connects them to the WAN. There is almost always a bandwidth constraint on the WAN and never in the LAN, therefore, it is more important to provide a differentiation of the types of traffic (e.g., real-time traffic, such as videoconference traffic, versus non-real-time traffic) over the WAN interfaces. If prioritization of real-time traffic over non-real-time traffic does not take place, and the amount of information to be transferred across the WAN link is greater than the available bandwidth, then congestion will occur resulting in a non-selective dropping of packets. The LAN usually relies upon the excess amounts of bandwidth available to guarantee that congestion will not take place.
Accordingly, it would be desirable and highly advantageous to have way to provide a guaranteed amount of bandwidth for a videoconference session, so as to avoid undesirable effects such as, e.g., non-selective dropping of packets.